Method for repairing a photomask, method for inspecting a photomask, method for manufacturing a photomask, and method for manufacturing a semiconductor device

ABSTRACT

A method for inspecting a photomask, comprising generating a laser beam, changing a phase of the laser beam to smooth the brightness distribution of the laser beam, applying the smoothed laser beam to the photomask, acquiring an image of the photomask using a sensor while the laser beam and the photomask are relatively moved, examining the image of the photomask for a defect of the mask-pattern of the photomask.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation-in-Part application of U.S. patent applicationSer. No. 09/263,937, filed Mar. 8, 1999, now abandoned which is aContinuation-in-Part application No. 09/105,031, filed Jun. 25, 1998,now abandoned, the entire contents of which are incorporated herein byreference.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 9-171695, filed Jun. 27,1997; No. 10-178300, filed Jun. 25, 1998; and No. 10-201942, filed Jul.16, 1998, the entire contents of all of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a method for repairing a photomask usedin manufacturing a semiconductor device comprising the step ofinspecting the mask-pattern of the photomask and then repairing anydefects in the mask-pattern on the basis of the inspection result.

An inspecting apparatus, used during the process for manufacturing asemiconductor devise, inspects for defects in the mask-pattern of aphotomask. This apparatus has an optical system for illuminating andimaging a photomask, a sensor for acquiring the image of the photomaskand outputting an image signal, and an inspection portion for inspectingthe mask-pattern on the basis of the outputted image signal.

As a light source used in the optical system, a mercury lamp isgenerally used. The mercury lamp makes it possible to illuminate thephotomask by light having wavelengths from the visible range to theultra-violet range (around 365 nm).

Recently, the minuteness and the integrated scale of mask-patterns for aphotomask have increased, as the performance of a semiconductorapparatus becomes higher. This requires an apparatus for inspecting thephotomask to exhibit a higher resolution so as to detect smaller defectsin the mask pattern. It is necessary to shorten the wavelength of lightfrom the optical system to realize the higher resolving power. However,conventional mercury lamps cannot provide enough illumination intensity,in the short wave range, which can be used for the inspecting apparatus.Therefore, a laser such as an ultraviolet laser is used instead of themercury lamp.

However, when a laser beam provides a light source for the defectinspecting apparatus, interference fringes are generated from thecoherency of the laser. The generation of the interference fringescauses variations in the brightness of the acquired image outputted fromthe sensor; therefore, in inspecting any defect, it is impossible todecide whether this “variation” is generated from a defect in themask-pattern or from the coherence of the laser beam.

BRIEF SUMMARY OF THE INVENTION

Therefore, one object of the present invention is to solve theabove-mentioned problem caused when the laser beam is used for the lightsource of the apparatus for inspecting a pattern-defect of amask-pattern. Another object is to provide a pattern-defect repairingapparatus for inspecting with a higher resolving power. Another objectis repairing the defect.

According to the first aspect of the present invention, there isprovided a method for repairing a sample comprising:

-   -   generating a laser beam;    -   changing a phase of the laser beam to smooth the brightness        distribution of the laser beam, and applying the laser beam to        the sample;    -   acquiring an image of the sample with a Time Delay Integration        (TDI) sensor, and outputting an image signal from the TDI sensor        in accordance with relative movement of the laser beam and the        sample;    -   detecting a defect of the mask-pattern of the sample on the        basis of the image signal output from the TDI sensor;    -   specifying the position of the defect of the mask-pattern on the        basis of the result obtaining by the detecting step; and    -   repairing the defect of the mask pattern.

According to the second aspect of the present invention, there isprovided a method for inspecting a sample, comprising:

-   -   generating a laser beam;    -   changing a phase of the laser beam to smooth the brightness        distribution of the laser beam;    -   applying the smoothed laser beam to the sample;    -   acquiring an image of the sample using a Time Delay Integration        (TDI) sensor while the laser beam and the sample are relatively        moved; and    -   examining the image of the sample for a defect of the        mask-pattern of the sample.

According to the third aspect of the present invention, there isprovided a method for manufacturing a sample comprising:

-   -   forming a pattern onto the sample;    -   generating a laser beam;    -   changing a phase of the laser beam to smooth the brightness        distribution of the laser beam, and applying the smoothed laser        beam to the sample;    -   acquiring an image of the sample with a TDI sensor as the laser        beam and the sample are moved relatively;    -   acquiring a defect of the mask-pattern of the sample on the        basis of the image of the sample; and    -   when the defect of the mask-pattern is detected, specifying the        position of the defect of the mask-pattern, and repairing the        defect of the mask-pattern.

According to the fourth aspect of the present invention, there isprovided an apparatus for inspecting a sample comprising:

-   -   an illuminating optical system for changing a phase of a laser        beam to smooth the brightness distribution of the laser beam,        and for applying the smoothed laser beam to the sample;    -   a sensor for acquiring an image of the sample as the laser beam        and the sample move relatively;    -   a defect examination device for examining the image of the        sample for a defect of the mask-pattern of the sample.

According to the fifth aspect of the present invention, there isprovided a method for manufacturing a semiconductor device by using asample after inspecting the sample, comprising:

-   -   generating a laser beam;    -   changing a phase of the laser beam to smooth the brightness        distribution of the laser beam;    -   applying the smoothed laser beam to the sample;    -   acquiring an image of the sample using a time Delay Integration        (TDI) sensor while the laser beam and the sample are relatively        moved; and    -   examining the image of the sample for a defect of the        mask-pattern of the sample.

According to the sixth aspect of the present invention, there isprovided a method for manufacturing a semiconductor device by using asample after manufacturing the sample, comprising:

-   -   forming a pattern onto the sample;    -   generating a laser beam;    -   changing a phase of the laser beam to smooth the brightness        distribution of the laser beam, and applying the smoothed laser        beam to the sample;    -   acquiring an image of the sample with a TDI sensor as the laser        beam and the sample are moved relatively;    -   acquiring a defect of the mask-pattern of the sample on the        basis of the image of the sample; and    -   when the defect of the mask-pattern is detected, specifying the        position of the defect of the mask-pattern, and repairing the        defect of the mask-pattern.    -   examining the image of the sample for a defect of the        mask-pattern of the sample.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a schematic illustration of a first embodiment according tothe present invention;

FIGS. 2A to 2C are schematic illustrations of the first embodiment, eachof which shows a schematic view of a phase rotating plate;

FIGS. 3A and 3B are schematic illustrations of the first embodiment, andare an image plan showing interference fringes which occurs on a samplefor coherency of a laser beam, and a profile view of the wave form ofbrightness distribution, respectively;

FIG. 4 is schematic illustration for explaining the first embodiment,each of which shows the process for smoothing brightness by shifting theaxis of light;

FIG. 5 is a schematic illustration of the first embodiment and is aflowchart of the process of inspecting and repairing a mask;

FIG. 6 is a schematic illustration of a variation of the firstembodiment;

FIG. 7 is a schematic illustration of a second embodiment;

FIG. 8 is a schematic illustration of a third embodiment;

FIG. 9 is a schematic illustration of the third embodiment and shows afirst laser beam dividing unit;

FIG. 10 is a schematic illustration of the third embodiment and shows asecond laser beam dividing unit;

FIG. 11 is an illustration of the third embodiment showing the polarizeddirection of the laser beam after the first laser beam dividing unit;

FIG. 12 is an illustration of the third embodiment showing the polarizeddirection of the laser beam after the second laser beam dividing unit;

FIG. 13 is an illustration of the third embodiment showing the polarizeddirection of the laser beam of which polarization is partly rotated;

FIG. 14 is a schematic illustration showing a modification of the thirdembodiment;

FIG. 15 is a schematic illustration of the fourth embodiment;

FIG. 16 is a view for illustrating correction coefficients and referencedata;

FIG. 17 shows a state wherein the amplitude of an output signal of aTime Delay Integration (TDI) sensor coincides with the amplitude ofreference data after the amplitude of the reference data is corrected;

FIG. 18 is a schematic illustration of the fifth embodiment;

FIG. 19 is a view for showing an ideal speed of an XY table, andillustrating the variation of the speed of the XY table with inclinedarrows;

FIG. 20 is a schematic illustration of the sixth embodiment;

FIG. 21 is a schematic illustration of the seventh embodiment;

FIG. 22 is a schematic illustration of the eighth embodiment; and

FIG. 23 is a schematic illustration of the ninth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the attached drawings, first to sixth embodiments accordingto the present invention will now be described.

(First Embodiment)

FIG. 1 illustrates a mask-pattern inspecting apparatus and a maskrepairing apparatus 20 for repairing a mask on the basis of the resultsobtained from an inspection by the mask-pattern inspecting apparatus.

In FIG. 1, the reference number 1 denotes an XY table. The XY table 1supports a sample or photomask 2, an object for inspecting andrepairing, and can move the sample or photomask 2 in any XY direction.The XY table is connected to a central controlling portion 4 through adriver 3 for driving the XY table 1.

The inspecting apparatus also has an optical system 5 for illuminatingthe sample or photomask 2 supported by the XY table 1. The opticalsystem 5 comprises an Ar laser 6 as a laser beam emitting source, alaser beam smoothing optical system 7 for changing interference fringesof the laser beam to make the brightness distribution of the laser beamuniform, and a condenser lens 8 for illuminating the laser beam whichhas passed through the laser beam smoothing optical system 7 onto thesample or photomask 2.

The laser beam smoothing optical system 7 has an integrator lens 10 (forexample, a fly eye lens), a phase rotating plate 11, and a vibrationmirror 12.

The fly eye lens is one of the integrator lenses and has a structure inwhich many lenses 10 a are aligned in an array form. The fly eye lensforms secondary light source images. The pupil images of the secondarylight sources overlap each other on the sample or photomask 2 to smooththe intensity distribution of the laser beam 6.

FIG. 2A shows a phase shift plate 11 which can rotate. The phase shiftplate 11, illustrated in enlarged views, i.e., FIGS. 2B and 2C, is atransparent disc which consists of a large number of steps 11 a to 11 d.The steps 11 a to 11 d have different depths and are arranged at random.The phase shift plate 11 has different thickness at various points,Therefore, when the laser beam passes through the phase rotating plate11 while the plate 11 rotates, the phase of the laser beam changesdepending on the depth of the respective steps 11 a to 11 d. The steps11 a to 11 d to have such thickness that the phase of the laser beam isshifted by 0, ¼λ, ½λ and ¾λ, respectively, where λ is the wave length ofthe laser beam.

A rotationally-driving motor rotationally drives the phase rotatingplate 11, A motor driver, not illustrated, connects the motor 13 to acentral controlling portion 4. The central controlling portion 4controls the motor 13 so that the phase rotating plate 11 can be rotatedat, for example, 10,000 rpm.

When the phase of the laser beam changes at random in such a manner asabove, the interference fringes of the laser beam also change.Furthermore, carrying out this change at a high speed smoothes thebrightness of the laser beam.

The vibration mirror 12 can swing and vibrate by means of amechanically-driving unit 15 such as piezo element at, for example, 100Hz. The mirror 12 shifts the optical axis of the laser beam reflectingfrom the mirror 12.

Such a shift of the optical axis of the laser beam as above changes theinterference fringes of the laser beam, as described in FIGS. 3A and 3Band FIG. 4. FIG. 3A is an image plan showing the brightness distribution(interference fringes) of the laser beam emitted from the laser beamsource 1. FIG. 3B shows a wave profile view of the representing thebrightness distribution across section IIIB—IIIB of FIG. 3A.

Vibration of the vibration mirror 12 shifts the brightness distributionwave form shown in FIG. 3B in the lateral direction, as shown in FIG. 4.When the vibration mirror 12 vibrates with such an amplitude that thewidth of the shift will be less than a pitch l shown in the FIG. 4, orwill be inmultiples of l′, where l′ is a value less than l, at a highspeed, the brightness of the laser beam can be made uniform asillustrated in FIG. 4. The amplitude and the frequency of the vibrationmirror 12 can be decided and controlled by the central controllingportion 4.

As descried above, the laser beam through the vibration mirror 12 isapplied to the sample or photomask 2 through the condenser lens 8, underthe condition that the brightness of the laser beam is made uniform.

Furthermore, this apparatus has a Time Delay Integration sensor 17 (TDI)shown in FIG. 1 as a sensor for acquiring the image of the sample orphotomask 2. The TDI sensor comprises photoelectric elements of 64lines, each of which has 2048 pixels and is controlled by a sensorcircuit 18 shown in FIG. 1. The TDI sensor 17 integrates thephoto-signal storage of the lines to the neighboring line in turn. Whenthe total intensity signals of the 64 lines are integrated, the TDIsensor outputs the result.

The integration time for the TDI sensor 17 to store the signals (thesignal storing time) is identical to the time necessary for scanning thesame point of the sample or photomask 2 from the 1st line to 64th line.It is preferable to set the signal storing time to a minimum time whichmakes it possible to smooth the brightness of the laser beam by thesmoothing optical system 7.

According to the present embodiment, uniform signals which are notinfluenced by the coherency of the laser beam can be acquired, forexample, if in the step illustrated in FIG. 4 the signal storing timebecomes equal to the time required to shift the wave form of the lightof the interference fringe at least one pitch l.

On the contrary, the rotation number of the phase shift plate 11 and thevibration frequency of the vibration mirror 12 may be decided so as tomatch the signal integration time of the storage sensor 17.

Namely, when the signal storing time of the TDI sensor 17 is short, itis necessary to smooth the brightness of the laser beam within the shorttime, and thus, to increase the rotation velocity of the phase rotatingplate 11 and the vibration frequency of the vibration mirror 12.

In the present embodiment, uniform signals were able to be detected byrotating the phase shift plate 11 at 10,000 rpm, vibrating the vibrationmirror 12 at 100 Hz, scanning one line of the storage sensor in about 30μsec, and integrating the signal in about 30 μsec×64 (=1.92 msec).

In such a manner as above, the smoothing optical system 5 and the TDIsensor 17 illuminate the sample or photomask 2 and then detect the imagegenerated from the illumination, thereby enabling the acquisition of thephotomask or sample image without being affected by coherency.Accordingly, it becomes possible to detect the mask-pattern of thesample or photomask 2 with a high resolution.

The image of the mask-pattern detected as above is used for inspectionof the mask-pattern by the central controlling portion 4, and the resultobtained from the inspection is inputted into a mask repairing apparatus20 for repairing the mask-pattern.

The steps of this inspection and repair will be described as follows,with reference to a flowchart shown in FIG. 5.

Firstly, the system determines whether the pattern is formed at aposition as designed or not and whether the formed pattern has a defector not (step S1). Potential defects include lack of a part of thepattern (intrusion), remaining of unnecessary portions to be removed off(protrusion), and attachment of a particle.

After the completion of the inspection of the mask-pattern in the stepS1, the central controlling portion 4 specifies the position of eachdefect, and the type of the defect (step S2). In this step, either thedie-comparison method or the database pattern-comparison method can beused appropriately, as a method for inspecting for a pattern defect. Theformer is defined as the method of inspecting for defects by comparingneighboring identical, patterns, and the latter is defined as the methodof inspecting for defects by comparing data on the designed pattern withthe measured pattern.

The present embodiment adopts the designed pattern-comparison method. Adesigned data generating apparatus 21 is shown in FIG. 1. The inspectionis performed first by matching the position between the mask-patternimages obtained from the TDI sensor 17 and the position of the designedpattern image (CAD data) generated by the designed data generatingapparatus 21, and then comparing these images to detect defects with itsposition and the type.

When no defect is detected in the step S2, the inspection is finished(End). If a detected defect cannot be repaired, for example, when thedefects are large, located across neighboring patterns, or located at acorner point (step S3), the mask-pattern is removed from the photomaskor sample and patterned again (step S4).

After specifying the defect position and the type of defect in the stepS2, the central controlling portion 4 delivers the information to thephotomask or sample repairing apparatus 20 along with the sample orphotomask 2.

In the photomask or sample repairing apparatus, a suitable repairingmethod is carried out according to the type of defect. When the detecteddefect is decided to be an intrusion (step S5), a pattern is added tothe defect on the basis of the information of the defect position torepair it into a normal pattern (step S6). A pattern may be added, forexample, by a focused ion beam. When the defect is decided to be aprotrusion (step S7), an unnecessary pattern is removed on the basis ofthe information of the remaining-position by means of, for example, anelectronic beam or a laser beam (step 8).

When the defect is decided to be a particle (step S9), the sample orphotomask 2 is delivered to a washing step (step S10) to remove theparticle.

After the above-mentioned steps are carried out, the photomask or samplerepairing apparatus 20 delivers the sample or photomask 2 together withthe information on the defect-position to the photomask or sampleinspecting apparatus shown FIG. 1.

The inspection apparatus inspects the position of the defect repairingportion of the sample or photomask 2 based on the information of thedetected defect position, and inspects the acquired images according tothe step S2 again. According to one embodiment, only the position of thedefect is inspected. If necessary, the sample or photomask 2 isdelivered to the repairing apparatus 20 again and then the repairingprocess of the steps S4 to 10 is carried out.

The above-mentioned apparatus and steps make it possible to obtain aphotomask or sample pattern image which is not affected by coherency ofa laser and, as a result, to inspect with high precision. Furthermore, adefect on a sample or photomask 2 can be repaired according to theinformation having high precision.

The first embodiment has the vibration mirror 12 in the smoothingoptical system 7, however, similar advantages can be obtained even ifthe vibration mirror 12 is not provided.

FIG. 6 illustrates another example of the first embodiment. In thisembodiment, as well, the storing time of the TDI sensor 17 may bedetermined in accordance with the time during which the brightness ofthe laser beam can be made uniform by the rotation of the phase shiftplate.

On the contrary, the rotation velocity of the phase shift plate may bedetermined in accordance with the storing time of the TDI sensor.

(Second Embodiment)

The second embodiment according to the present invention will beexplained with reference to FIG. 7 as follows. The present embodimentillustrates another form of the smoothing optical system shown in FIG.1. Therefore, other parts are omitted in FIG. 7 and the same elements asin the first embodiment have the same reference numbers, And theexplanation of the other elements is also omitted.

A smoothing optical system 5′ has a fly eye lens 10, the first phaseshift plate 11′ positioned on the secondary light source image side ofthis fly eye lens 10, a relay optical system 22, and the second phaseshift plate 11″. The second phase shift plate 11″, and the first phaseshift plate 11′ sandwich the relay optical system 22, and the plate 11″is at the conjugate position from the plate 11′ relative to the relayoptical system 22.

As the first and second phase shift plates 11′ and 11″, the same plateas in the first embodiment may be used. The rotation direction of thephase rotating plate 11′ and 11″ should be the same because the image ofthe light source is reversed by the relay optical system 22.

This embodiment also makes it possible to change interference fringesand smooth the brightness of the laser beam in the same method as in thefirst embodiment because the laser beam passes through the fly eye lens10 to make the intensity distribution of the laser beam source uniformand subsequently the laser beam passes through the first and secondphase shift plates 11′ and 11″.

In this embodiment, the total of the rotation frequencies of the firstand second phase shift plates 11′ and 11″ may be the same rotationfrequency as that of the phase shift plate 11 in the first embodiment.As a result, the respective rotation frequencies of the plates 11′ and11″ can be made lower, thereby lightening the burden for the apparatus,

It is important for this embodiment that the rotation frequencies of thefirst and second phase rotating plates 11′ and 11″ and the rotationfrequency caused by the difference between them are not make identicalto the frequency of the proper vibration frequency of this apparatus.

(Third Embodiment)

The third embodiment of the present invention will be described, withreference to FIGS. 8 to 14, in the following.

This embodiment illustrates still another example of the smoothingoptical system in the first embodiment. Therefore, other parts areomitted in FIG. 8.

It is assumed that a linear polarized laser beam is emitted from a lasersource 6 and the diameter of the laser beam is 2L.

This laser beam is projected into the beam dividing unit 31. As shown inFIG. 9, the unit 31 divides the laser beam into an upper part and alower part and passes the upper part therethrough. And the unit 31detours the lower laser beam by reflecting it on mirrors 31 a, 31 b, 31c, and 31 d inclined at 45 degrees against the lower ray bundle. Also,the path length of the detoured laser beam is set so that it will belonger than the non-detoured path length plus the coherency distance ofthe laser. At the front of the mirror 31 d, the upper and lower laserbeams are combined.

This laser beam dividing unit 31 divides the laser beam into the upperand lower parts at the position A in FIG. 8 of the mirror 31 d,illustrated in FIG. 11.

The second laser beam dividing unit 32 is provided at the downstreamposition of the beam dividing unit 31. As shown in FIG. 10, the unit 32divides the incident laser beam into a right part and a left part andpasses the left laser beam as it is therethrough. And the unit 32detours the right laser beam by reflecting it on mirrors 32 a, 32 b, 32c, and 32 d inclined at 45 degrees against the right laser beam. Also,the path length of the detoured laser beam is set so that it will belonger than the non-detoured path length plus the coherency distance ofthe laser.

The laser beam which has passed through the first and second beamdividing units 30 and 31 as above is divided into four portions b1-b4,which do not interfere with each other above, below, right, and left, asshown in FIG. 12, at the downstream position B (see FIG. 1) of themirror 32 d.

A reflecting mirror 33 is provided at the down-stream of the beamdividing unit 32. The reflecting mirror 33 bends the laser beam 90degrees,

The laser beam reflected by the reflecting mirror 33 is projected into ahalf wave plate 34 which rotates the polarized direction of a part ofthe laser beam 90 degrees.

Accordingly, the polarized direction of the laser beam which has passedthrough this half wave plate 34 is as illustrated in FIG. 13.

A fly eye lens 35, downstream of the half wave plate 34, removes theinterference effect of the laser beam.

A phase rotating plate 36 is downstream of the fly array lens 35. Amotor(not shown) rotates the phase rotating plate 35. The phase rotatingplate 36 has the same structure as in the first embodiment and afunction of changing interference fringes of the laser beam.

The laser beam which has passed through the phase rotating plate 36 isbent 90 degrees by a reflecting mirror 37.

The laser beam reflected from the reflecting mirror 37 is condensed by acondenser lens 38 and concentrated on an object lens 39. Furthermore,the beam is concentrated by the object lens 10 to form a spot 41 on amask-pattern 40.

In this structure the coherency of the laser beam can be decreased bydetouring a part of the laser beam so as to make the light pathsdifferent or rotating a part of the laser beam. Furthermore, passingthis resultant laser through the phase rotating plate produces a uniformthe brightness. Thus, substantially the same advantages as obtained bythe first embodiment can be obtained.

This structure also permits the laser beam to be divided into four raybeams which do not interfere with each other by only 8 mirrors, so as toimprove structural efficiency and light-transmitting efficiency.

If a prism 42 with a wedge form, as shown in FIG. 14, is arranged in thefront of the half wave plate 34 shown in FIG. 8, speckles can be furtherdecreased.

This prism 42 of a wedge form may be arranged not in the front of thehalf wave plate 34 but in the rear of it.

The invention described above makes it possible to solve the problemwhich occurs when a laser beam is adopted as a light source of anapparatus for inspecting a pattern defect and to examine the patterndefect with a higher resolving power so as to repair the defect of aminute mask-pattern.

(Fourth Embodiment)

The fourth embodiment according to the present invention will beexplained with reference to FIGS. 15 to 17.

This embodiment relates to another example of the inspecting apparatusshown in FIG. 1, using the TDI sensor 17. With respect to the fourthembodiment, structural elements identical to those in FIG. 1 will bedenoted by the same reference numerals, and their detailed explanationswill be omitted. Furthermore, the fourth to sixth embodiments includemethods and apparatuses obtained by combining the first to thirdembodiments.

The apparatus according to the fourth embodiment is provided to correctthe variation of the amplitude of an output signal which occurs when theline width of the sample or photomask 2 varies, and thus prevent anerror of determination with respect to whether or not the sample orphotomask 2 is defective.

Another object of the apparatus is to prevent an error of determinationwhether or not the sample or photomask 2 is defective, when an erroroccurs in the speed of the XY table during measurement.

FIG. 15 is a block diagram of the inspecting apparatus using the TDIsensor 17. Reference to FIG. 15, the TDI sensor 17 comprises only oneline sensor. However, FIG. 15 shows this as a matter of convenience.Actually, the TDI sensor 17 has the same structure as that of the firstembodiment, which comprises a plurality of line sensors.

The sample or photomask 2, e.g., a semiconductor wafer, is provided onthe XY table 1, and the XY table 1 is moved by the driver 3 in adirection indicated by an arrow α.

On the other hand, the central controlling portion 4 receives an imagesignal output from the TDI sensor 17, and compares with the image signalwith reference data, to thereby inspect the pattern of the sample orphotomask 2. Whereas a main controlling portion 112 comprises a CPU,etc., the central controlling portion 4 comprises an outputting portion113, a line width inputting portion 114, a sensor data storing portion115, and a reference data holding portion 116, all connected to eachother. Furthermore, the central controlling portion 4 includes areference data correcting portion 118 and a comparing portion 119, whichoperate in response to a command given by the main controlling portion112.

The outputting portion 113 has a function of transmitting a movementcommand generated from the main controlling portion 112. The line widthinputting portion 114 is one of various kinds of inputting devices suchas a keyboard and a mouse, and fetches line width data of the maskpattern formed on the sample or photomask 2.

The sensor data storing portion 115 serves to store the image signaloutput by the TDI sensor 17. The reference data holding portion 116holds reference data (design patterns) which is used as comparison datawhen the sample or photomask 2 is inspected.

The correction coefficient holding portion 117 holds correctioncoefficients for use in correcting the amplitude of the image signalwith respect to the line width of the mask pattern of the sample orphotomask 2. The correction coefficient is applied to an image signalrepresenting the mask pattern of the sample or photomask 2, when theimage signal is compared with the reference data.

The correction coefficient is determined as follows:

-   -   First of all, a couple of samples or photomasks 2 each of them        having a known mask pattern are prepared. It is moved in such a        manner as to be scanned by the TDI sensor 17. Then, the maximum        and minimum values of the output signal of the TDI sensor 17 are        measured. The amplitude of the image signal is calculated from        the measured maximum and minimum values, the amplitude changes        corresponding to the variation of the line width of the mask        pattern of the sample or photomask 2, which is measured by use        of the TDI sensor 17.    -   Next correction coefficients for use in making the reference        data corresponding to each line width of the mask patterns        coincide with the image signal output by the TDI sensor 17 are        determined by use of the above amplitude and maximum and minimum        values. Then, they are tabled. FIG. 16 shows the relationship        between the line width and the correction coefficient of the        reference data. As shown in FIG. 16, the smaller the line width,        the smaller the correction coefficient.

The reference data correcting portion 118 receives line width data ofthe sample or photomask 2 which is fetched by the line width inputtingportion 114, and reads out a correction coefficient corresponding to thereceived line width data, from the correction coefficient holdingportion 117. Then, with respect to the line width, the reference datacorrecting portion 118 corrects in real time the reference data which issuccessively read out while the XY table 1 is being moved, by use of theread-out correction coefficient.

The comparing portion 119 compares the image signal of the TDI sensor 17with the reference data corrected by the reference data correctingportion 118, to thereby inspect the sample or photomask 2.

Next, the inspecting operation of the apparatus having the abovestructure will be explained as follows:

-   -   when a sample or photomask 2 such as a semiconductor wafer is        determined, the line width data of the sample or photomask 2 is        input from the line width inputting portion 114. The line width        data is sent to the reference data correcting portion 118 in        response to the command from the main controlling portion 112.    -   When the sample or photomask 2 is placed on the XY table 1, and        the driver 3 is operated in response to the command from the        main controlling portion 112, the XY table 1 is moved in the        direction indicated by the arrow α, with the sample or photomask        2 provided on the XY table 1.

At this time, the TDI sensor 17 receives light from the sample orphotomask 2 on the XY table 1 at regular intervals while the sample orphotomask 2 thereon is being moved, and successively accumulates signalsrepresenting the intensities of the light from the sample or photomask2. The signals accumulated by the TDI sensor 17 are successively outputtherefrom and stored as data in the sensor data storing portion 115.

The comparing portion 119 receives the signals successively output fromrespective line sensors of the TDI sensor 17, and successively reads outand develops reference data from the reference data holding portion 116while the XY table 1 is being moved. Then, the comparing portion 119successively compares the above output signals of the TDI sensor 17 andthe reference data.

FIG. 17 illustrates that inconsistency of the output signal of the TDIsensor 17 and the reference data which occurs in the cases where theline width of the sample or photomask 2 is great, and where it is small.As shown in FIG. 17, when the line width of the sample or photomask 2 isequal to a predetermined line width, the amplitude of the output signalof the TDI sensor 17 coincides with the amplitude of the reference data.However, when the line width of the sample or photomask 2 is greaterthan the predetermined line width, the amplitude of the output signal ofthe TDI sensor 17 is greater than the amplitude of the reference data.In contrast, when the line width of the sample or photomask 2 is smallerthan the predetermined line width, the amplitude of the output signal ofthe TDI sensor 17 is smaller than that of the reference data. In such acase, even when the mask pattern of the sample or photomask 2 coincideswith the mask pattern represented by the reference data, there is apossibility that the sample or photomask 2 may be regarded as adefective one. This is because the amplitude of the output signal of theTDI sensor 17 does not coincide with that of the reference data.

In view of the above, according to the present invention, when thecomparing portion 119 performs the above-mentioned comparing operation,the reference data correcting portion 118 receives the line width dataof the sample or photomask 2 which is fetched by the line widthinputting portion 114, reads out a correction coefficient correspondingto the received line width data from the correction coefficient holdingportion 117, and corrects the amplitude of the reference data, whichvaries in accordance with the moved position of the XY table 1, by usingthe read-out correction coefficient.

The comparing portion 119 compares the output signal of the TDI sensor17 and the reference data corrected by the reference data correctingportion 118. Then, it determines that the sample or photomask 2 isnon-defective, when the amplitude of the output signal of the TDI sensor17 coincides with that of the reference data, and determines that thesample or photomask 2 is defective, when the amplitude of the outputsignal of the TDI sensor 17 does not coincide with that of the referencedata.

By virtue of such a structure, even if the line width of the sample orphotomask 2 varies, and in particular, even if it varies slightly, theamplitudes of the output signals of the TDI sensor 17 do not coincidewith that of the reference data. Thus, the apparatus does not make anerror in determination on whether or not the sample or photomask 2 isdefective. Therefore, it can inspect the sample or photomask 2 with highaccuracy.

(Fifth Embodiment)

Next, the fifth embodiment will be explained with reference to FIG. 18.With reference to the fifth embodiment, structural elements identical tothose in FIG. 15 will be denoted by the same reference numerals, andtheir detailed explanations will be omitted.

FIG. 18 is a block diagram of an inspecting apparatus according to thefifth embodiment.

According to this embodiment, the central controlling portion 4 fetchesthe output signal of the TDI sensor 17, and compares the output signalwith the reference data, to thereby inspect the pattern of the sample orphotomask 2. The central controlling portion 4 includes a speedvariation detecting portion 122 and a read development correctingportion 123, which operate in response to a command given by a maincontrolling portion 121 comprising a CPU, etc.

The speed variation detecting portion 122 detects the variation of therelative speed of the sample or photomask 2 to the TDI sensor 17, i.e.,the variation of the speed of the XY table 1. To be more specific, itcompares the average speed of the XY table 1 moved before a lapse of apredetermined time period, with the present speed of the XY table 1, tothereby detect the variation of the speed of the XY table 1.

The read development correcting portion 123 corrects the timing at whichthe reference data is read out and developed from the reference dataholding portion 116, in accordance with the variation of the speed ofthe XY table 1 which is detected by the speed variation detectingportion 122. To be more specific, the read development correctingportion 123 corrects the above timing such that the reference data isread and developed at an earlier timing, when the speed of the XY table1 is high, and corrects the timing such that the reference data is readout and developed at a later timing, when the speed of the XY table 1 islow.

The inspecting operation of the apparatus having the above structurewill be explained.

When the sample or photomask 2 is placed on the XY table 1, and thedriver 3 is operated in response to a command from the main controllingportion 121, the XY table 1 is moved in a direction indicated by anarrow α, with the sample or photomask 2 provided on the XY table 1.

At this time, while the sample or photomask 2 is being moved, the TDIsensor 17 receives light intensities, from the sample or photomask 2 onthe XY table 1, and accumulates those intensities as signals. Then, theTDI sensor 17 successively outputs the accumulates signals from its linesensors, respectively. The output signals of the TDI sensor 17 aresuccessively stored as data in the sensor data storing portion 115.

The speed variation detecting portion 122 fetches an (n−1) number ofdata respectively representing the past speeds of the XY table 1 whichhave been detected before a predetermined time period lapses, anddetermines the average speed of the XY table 1 from the (n−1) number ofdata. Then, the speed variation detecting portion 122 compares theaverage speed with the reference data to detect the variation of thespeed. FIG. 19 shows an ideal speed of the XY table 1, and illustratesthe variation of the speed of the XY table 1 with inclined arrows.

The read development correcting portion 123 corrects the timing at whichthe reference data is read and developed from the reference data holdingportion 116, in accordance with the variation of the speed which isdetected by the speed variation detecting portion 122. For example, theread development correcting portions 123 corrects the above timing suchthat the reference data is read and developed at an earlier timing, whenthe speed of the XY table 1 is high, and corrects the timing such thatthe reference data is read and developed at a later timing, when thespeed of the XY table 1 is low.

By virtue of the above feature, even if the speed of the XY table 1varies, the positions thereof represented by the signals respectivelyoutput from the line sensors of the TDI sensor 17 coincide with thepositions represented by the reference data which is successively readand developed.

The comparing portion 119 compares the signals which are successivelyoutput from the line sensors of the TDI sensor 17, respectively, withthe reference data the read and development timing of which iscorrected, at which the reference data is read and developed from thereference data holding portion 116. The comparing portion 119 determinesthat the sample or photomask 2 is non-defective, when the speedsrepresented by the above signals coincide with the speeds represented bythe reference data, and determines that the sample or photomask 2 isdefective, when the former speeds do not coincide with the latterspeeds.

In such a manner, according to the fifth embodiment, even if the speedof the XY table 1 varies, the positions represented by the referencedata read and developed can be made to coincide with those representedby the signals successively output from the line sensors of the TDIsensor 17, and thus the sample or photomask 2 can be inspected with highaccuracy. In particular, the inspecting apparatus according to the fifthembodiment overcomes the following disadvantage of conventionalinspecting apparatuses:

-   -   If the pattern of the sample or photomask 2 has lines each of a        large width, inspection of the sample or photomask 2 is not        greatly influenced by the pattern. However, if the pattern has        lines each of a small width, inspection of the sample or        photomask 2 is influenced by the pattern.

Such a problem does nor arise in the apparatus according to the fifthembodiment. Thus, the apparatus can inspect the sample or photomask 2with high accuracy.

(Sixth Embodiment)

The sixth embodiment will be explained with reference to FIG. 20. Withrespect to the sixth embodiment, structural elements identical those inFIGS. 15 and 18 will be denoted by the same reference numerals, andtheir explanations will be omitted.

FIG. 20 is a block diagram of the inspecting apparatus having the TDIsensor 17. The inspecting apparatus is a combination of the apparatusesaccording to the fourth and fifth embodiments.

By virtue of such a structure (the above combination), the line widthdata of the sample or photomask 2 is input from the line width inputtingportion 114, and sent to the reference data correcting portion 118 inresponse to the command of the main controlling portion 112.

When the sample or photomask 2 is placed on the XY table 1, and the XYtable 1 is moved in a direction indicated by an arrow α, the TDI sensor17 receives light from the sample or photomask 2, and accumulatessignals representing the intensities of the light. Then, the linesensors of the TDI sensor 17 successively outputs the accumulatedsignals, respectively. Those output signals are successively stored asdata in the sensor data storing portion 115.

The speed variation detecting portion 122 determines the average speedof the XY table 1 moved before a predetermined time period lapses, andcompares the average speed and the present speed of the XY table 1 todetect the variation of the speed.

The read development correcting portion 123 corrects the timing at whichthe reference data is read and developed from the reference data holdingportion 116, in accordance with the detected variation of the speed.

The reference data correcting portion 118 receives the line width dataof the sample or photomask 2 which is fetched by the line widthinputting portion 114, and reads out the correction coefficientcorresponding to the received line width data, from the correctioncoefficient holding portion 117. Then, the reference data correctingportion 118 corrects in real time the amplitude of the reference dataread and developed by the read development correcting portion 123 by useof the read-out correction coefficient.

The comparing portion 119 compares the signals successively output fromthe respective line sensors of the TDI sensor 17 with the reference datawhich is read out from the reference data holding portion 116, and theamplitude of which is corrected by the reference data correcting portion118. The comparing portion 119 determines that the sample or photomask 2is non-defective, when the output signals of the TDI sensor coincidewith the reference data, and determines that the sample or photomask 2is defective, when the output signals do not coincide with referencedata,

In such a manner, according to the sixth embodiment, even if the linewidth of the sample or photomask 2 varies, and in particular, the linewidth varies slightly, the output signals do not coincide with thereference data with respect to the amplitude. Thus, the apparatus doesnot make an error of determination with respect to whether or not thesample or photomask 2 is defective. Furthermore, even if the speed ofthe XY table 1 varies, the positions of the reference data which is readand developed in accordance with the speed of the table 1 can be made tocoincide with the positions of the signals successively output from therespective line sensors of the TDI sensor 17. Therefore, inspection ofthe sample or photomask 2 can be performed with high accuracy.

(Seventh Embodiment)

The inspection apparatus according to the seventh embodiment will beexplained with reference to FIG. 20. With respect to the seventhembodiment, structural elements identical those shown in FIG. 1 will bedenoted by the same reference numerals, and their explanations will beomitted.

The inspection apparatus of the seventh embodiment is featured in thatits inspection means is made of a sensor 200 other than a TDI sensor.The sensor 200 is, for example, a camera-type sensor wherein elementsare arranged in two dimensions, as in a CCD camera. Alternatively, a CCDline sensor having elements arranged in one dimension may beadditionally employed. The camera-type sensor and the CCD line sensorhave a signal accumulation function. During the accumulation of signals,interference patterns are changing constantly, and signals representingthe interference patterns are averaged to obtain a pattern image free ofinterference noise.

When the camera-type sensor and the CCD line sensor are employed assensors 200, signals representing constantly-changing interferencepatterns are averaged. By this averaging operation, interference noiseis removed from a pattern image to be obtained.

The structure of the seventh embodiment enables formation of a photomaskor sample image that is not adversely affected by the coherence of alaser beam. The photomask or sample image ensures highly reliableinspection. In addition, a defect of a photomask or sample can berepaired, referring to highly-reliable defect information.

Point-type sensors, such as a photodiode (PD) and a photomultiplier(PMT), may be employed. When sensors of this type are used, theinspection optical system may be the same as that used when the TDIsensor is used. The point-type sensors are non-accumulation typesensors, and when they are used, signals representingconstantly-changing interference patterns are averaged to obtain apattern image free of interference noise.

As described above, the sensors applicable to the inspection apparatusof the present invention are not limited to TDI sensors; they may be acamera-type sensor, a CCD line sensor, a photodiode, a photomultiplier,etc.

(Eighth Embodiment)

The inspection apparatus according to the eighth embodiment will beexplained with reference to FIG. 22. With respect to the eighthembodiment, structural elements identical those shown in FIGS. 1 and 21will be denoted by the same reference numerals, and their explanationswill be omitted.

The eighth embodiment is an embodiment wherein a sample other than aphotomask or sample is inspected. The sample may be a wafer, a liquidcrystal panel, an element-mounted board, or the like. Since thesesamples do not allow transmission of light, a reflection-type opticalsystem is used for the inspection. That is, light reflected by thesurface of a sample is reflected in such a manner that the reflectedlight travels in a direction perpendicular to the optical path ofilluminating light. The reflected light enters a focusing lens 212, bywhich it is made to fall on a sensor 200. In FIG. 22, reference numeral211 denotes a relay lens system.

As described above, the sample inspected by the inspection apparatus isnot limited to a photomask or sample; it may be a wafer, a liquidcrystal panel, an element-mounted board, or the like.

(Ninth Embodiment)

The inspection apparatus according to the ninth embodiment will beexplained with reference to FIG. 23. With respect to the ninthembodiment, structural elements identical those shown in FIGS. 1, 21 and22 will be denoted by the same reference numerals, and theirexplanations will be omitted.

According to the ninth embodiment, the illuminating optical system, bywhich a sample is illuminated, employs an illuminating-system pupilfilter 220. The characteristics of this illuminating-system pupil filter220 can be determined in a desirable manner. For example, the shape alight beam has after transmission, transmittance distribution, phase,etc. can be adjusted. In addition, the focusing system employs apower-variable lens assembly 221. Owing to the use of these, a samplepattern can be projected on the sensor under a desired magnification.

The power-variable lens assembly 221 can employ a focusing-system pupilfilter 222. The characteristics of this focusing-system pupil filter 222can be determined in a desirable manner as above. By properly adjustingthe characteristics of the illuminating-system pupil filter 220 and thefocusing-system pupil filter 222, a pattern image can be adjusted incharacteristics. The characteristics of the illuminating-system pupilfilter 220 and the focusing-system pupil filter 222 can be so determinedas to emphasize a pattern defect.

The present invention includes a semiconductor device manufactured byuse of a photomask or sample inspected, repaired and formed according tothe first to sixth embodiments, and a method for manufacturing thesemiconductor device by use of the photomask or sample.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A method of repairing a sample comprising: generating a laser beam;changing a phase of the laser beam to smooth the brightness distributionof the laser beam, and applying the laser beam to the sample; acquiringan image of the sample with a sensor, arid outputting an image signalfrom the sensor in accordance with relative movement of the laser beamand the sample; detecting a defect of a pattern of the sample on thebasis of the image signal output from the sensor; specifying theposition of the defect of the pattern on the basis of the resultobtained by the detecting step; and repairing the defect of the pattern.2. A method for repairing a sample according to claim 1, wherein asignal integration time of the sensor is enough for smoothing thebrightness distribution of the laser beam in the step of changing.
 3. Amethod for repairing a sample according to claim 1, wherein a laser beamsource used in the generating step is a source which can continuously orintermittently emit a laser beam.
 4. A method for repairing a sampleaccording to claim 1, wherein the changing step includes the step ofchanging the optical axis or the laser beam against the samplecontinuously or intermittently to change interference fringes of thelaser beam, thereby smoothing the brightness distribution of the laserbeam.
 5. A method for repairing a sample according to claim 4, whereinthe period when the optical axis of the laser beam is changed againstthe sample is decided in accordance with the signal integration time ofa sensor.
 6. A method for repairing a sample according to claim 1,wherein the changing step includes the step of passing the laser beaminto a rotating phase shift plate which has different thickness points,to change the phase of the laser beam, thereby smoothing the brightnessdistribution of the laser beam.
 7. A method for repairing a sampleaccording to claim 6, wherein the rotation velocity of the phase shiftplate is enough for signal integration of the sensor.
 8. A method forrepairing a sample according to claim 6, wherein the changing stepincludes the step of passing the laser beam into a plurality of rotatingphase shift plates.
 9. A method for repairing a sample according toclaim 8, wherein the total rotation rate of the phase shift plates isenough for smoothing the brightness for the signal integration of thesensor.
 10. A method for repairing a sample according to claim 1,wherein the changing step includes a first step of detouring a part ofthe laser beam, and a second step of detouring the part of the laserbeam detoured in the first detouring step, in a different direction fromthe detour of the first detouring step; thereby dividing the laser beamto reduce the coherency of the laser beam and smooth the brightnessdistribution of the laser beam.
 11. A method for repairing a sampleaccording to claim 1, wherein the changing step includes a first step ofdetouring about one-half of the laser beam, and a second step ofdetouring the half of the laser beam detoured in the first detouringstep, in a direction inclined at 90 degrees against the detour directionin the first detouring step; thereby dividing the laser beam into fourbeams which do not interfere with each other, to reduce the coherency ofthe laser beam and make uniform the brightness distribution of the laserbeam.
 12. A method for repairing a sample according to claim 10, whereinthe path length difference between the total path length in the firstdetouring step and in the second detouring step and the path length ofthe laser beam not detoured in a coherency distance or more, therebydividing the laser beam into four ray beams which do not interfere witheach other.
 13. A method for repairing a sample according to claim 10,further including the step of providing a half wave plate for rotating,at 90 degrees, the polarized direction of a part of the laser beam, thepart including the center of the laser beam, the part including thecenter or the laser beam, among the laser beams which have been detouredvia the second detouring step.
 14. A method for repairing a sampleaccording to claim 13, wherein a prism with a wedge form is provided inthe front or in the rear of the half wave plate.
 15. A method forrepairing a sample according to claim 1, further including the step ofoutputting the image signal output from the sensor after correcting theimage signal by use of a correction coefficient associated with a linewidth of the pattern of the sample.
 16. A method for repairing a sampleaccording to claim 1, wherein in the detecting step, the image signaloutput from the sensor is compared with reference data which is readout, to thereby detect whether or not the pattern has a defect.
 17. Amethod for repairing a sample according to claim 16, further includingthe step of detecting a relative speed of the sample to the sensor, andcorrecting timing at which the reference data is read out, in accordancewith the relative speed.
 18. A method for inspecting a sample,comprising: generating a laser beam; changing a phase of the laser beamto smooth the brightness distribution of the laser beam; applying thesmoothed laser beam to the sample; acquiring an image of the sampleusing a sensor while the laser beam and the sample are relatively moved;and examining the image of the sample for a defect of a pattern of thesample.
 19. A method for inspecting a sample according to claim 18,wherein a signal integration time of the sensor is enough for smoothingthe brightness distribution of the laser beam in the step of changing.20. A method for inspecting a sample according to claim 18, wherein thelaser beam used in the generating step is a source which cancontinuously or intermittently emit a laser beam.
 21. A method forinspecting a sample according to claim 18, wherein the changing stepincludes the step of changing the optical axis of the laser beam againstthe sample continuously or intermittently to change interference fringesof the laser beam thereby smoothing the brightness distribution of thelaser beam.
 22. A method for inspecting a sample according to claim 21,wherein the period when the optical axis of the laser beam is changedagainst the sample is decided in accordance with the signal integrationtime of the sensor.
 23. A method for inspecting a sample according toclaim 18, wherein the changing step includes the step of passing thelaser beam into a rotating phase shift plate which has differentthickness points, to change the phase of the laser beam, therebysmoothing the brightness distribution of the laser beam.
 24. A methodfor inspecting a sample according to claim 23, wherein the rotationvelocity of the phase shift plate is enough for the signal integrationof the sensor.
 25. A method for inspecting a sample according to claim23, wherein the changing step includes the step of passing the laserbeam into a plurality of rotating phase shift plates.
 26. A method forinspecting a sample according to claim 25, wherein the total rotationrate of the phase shift plates is enough for smoothing the brightnessfor the signal integration of the sensor.
 27. A method for inspecting asample according to claim 18, wherein the changing step includes a firststep of detouring a part of the laser beam and a second step ofdetouring the part of the laser beam detoured in the first detouringstep, in a different direction from the detour of the first detouringstep; thereby dividing the laser beam to reduce the coherency of thelaser beam and smooth the brightness distribution of the laser beam. 28.A method for inspecting a sample according to claim 18, wherein thechanging step includes a first step of detouring about one-half of thelaser beam, and a second step of detouring the half of the laser beamdetoured in the first detouring step, in a direction inclined at 90degrees against the detour direction in the first detouring step;thereby dividing the laser beam into four beams which do not interferewith each other, to reduce the coherency of the laser beam and makeuniform the brightness distribution of the laser beam.
 29. A method forinspecting a sample according to claim 27, wherein the path lengthdifference between the total path length in the first detouring step endin the second detouring step and the path length of the laser beam notdetoured is a coherency distance or more, thereby dividing the laserbeam into four ray beams which do not interfere with each other.
 30. Amethod for inspecting a sample according to claim 27, further includingthe step of providing a half wave plate for rotating, at 90 degrees, thepolarized direction of a part of the laser beam, the part including thecenter of the laser beam, among the laser beams which have been detouredvia the second detour step.
 31. A method for inspecting a sampleaccording to claim 30, wherein a prism with a wedge form is provided inthe front or in the rear of the half wave plate.
 32. A method forinspecting a sample according to claim 18, further including the step ofoutputting the image signal output from the sensor after correcting theimage signal by use of a correction coefficient associated with a linewidth of the pattern of the sample.
 33. A method for inspecting a sampleaccording to claim 18, wherein in the examining step, a signal outputfrom the sensor is compared with reference data which is read, tothereby detect whether or not the pattern has a defect.
 34. A method forinspecting a sample according to claim 33, further including the step ofdetecting a relative speed of the sample to the sensor, and correctingtiming at which the reference data is read, in accordance with therelative speed.